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December 2009

December 28, 2009

Agriculture is a problem as well as a potential solution. It is responsible for 14% of global GHG emissions or 6.8 Gt of CO2e per year (per FAO), but it also has high mitigation potential (up to 6 Gt of CO2e per year by 2030) primarily through soil carbon sequestration. About 74% of emissions from agriculture originate in developing countries, and 70% of the mitigation could be realized in the same regions. The key is to build organic matter in soils and keep it there for the long term. In addition, fertilizer use, rice production and livestock management all offer further mitigation potential for non-carbon GHG emissions.

Combined with the emissions from deforestation (12-17%), at least a quarter of annual global GHG emissions can be traced to agriculture and land-use changes driven by agriculture and logging. It appears that COP15 did make some progress in tackling emissions from deforestation and agriculture. An international working group is to be formed to devise ways to mitigate emissions from agriculture, and countries would be compensated for preserving forests and other natural landscapes.

Progress is hard and COP15 disappointed a lot of people, but these were a couple of bright spots to emerge from the chaos.

December 17, 2009

As the world struggles to put together even a minimally substantive climate change agreement in Copenhagen, a leaked analysis from the UN points out that annual GHG emissions will need to peak between 2015 and 2020, and decline thereafter, in order to eventually stabilize the atmospheric CO2 concentration at 450 ppm. This is the concentration at which the temperature increase is likely to stay within 2 deg C. Current pledges of maximum emission reductions and voluntary actions, if achieved, would still result in annual emissions in 2020 being about 1.9 Gt over the recommended limit. This gap increases to 4.2 Gt if the upper range of pledges are not achieved. If the peak occurs later than 2020, the CO2 concentration could exceed 550 ppm with a corresponding temperature increase of around 3 deg C -- based on the optimistic 1.9 Gt gap.

This is basically a case of a potentially very dire outcome coupled with weak solutions. Rosemary Randall writes that climate change discourses present two parallel narratives. Narratives about the problem of climate change suggest losses on a terrifying scale that may happen far in the future or in distant lands. Narratives about solutions revolve around bland and ineffective solutions, mostly ignoring the scale of potential losses in the future. Ineffective solutions are not just the domain of governments -- a recent AP-Stanford University poll shows that three-quarters of respondents would support action to address climate change, but 59% wouldn't support any action if it costs them an additional $10 a month on electricity charges (which by the way is just about what it costs extra to purchase green electricity where I live).

The disconnect between the scale of the problem and the effectiveness of the solutions is alarming.

December 08, 2009

A very interesting front-page article in The Oregonian on the science and politics of using forests to mitigate climate change. It turns out to be a complex optimization problem. Trees, of course, sequester carbon, but thinning out the stands might help store more carbon in the long run by reducing the intensity of forest fires. On the other hand, letting young trees mature would actively take carbon out of the atmosphere during the growth phase. Logging mature trees and turning them into lumber could store carbon in long-lived wood products (of course, some carbon would be released from decomposition or burning of waste generated during logging and manufacturing). Undisturbed soil under forest cover could store significant amounts of carbon for long periods of time. My guess is that the right way to structure a forest will vary from place to place, depending on the tree species, climate and a host of other factors. Has anyone formulated this as a proper optimization problem?

December 04, 2009

Facebook just announced that it now has over 350 million users with half of them logging on to the site on any given day, and the average user spends over 55 minutes a day on Facebook. Plus, 55 million status updates are posted every day and 2.5 billion photos are uploaded each month. Very impressive, but I have often wondered about the environmental impact of social networking. Using carbon footprint as a proxy for overall environmental impact, here is a quick back-of-the-envelope calculation.

The number of user-hours per day is about 160 million (assuming 55 minutes/day/user). I found a CO2 emissions estimate of 20 mg/second for basic web browsing, most of it coming from the electricity consumed by the visitor's computer. I independently verified this by assuming 100 W of power consumption for a typical desktop computer and monitor in active mode, which translates to roughly 20 mg of CO2e per second for US average electricity (cradle to grid). Electricity emissions vary around the world, but the US emission factor is a typical value. For a first-order estimate, I decided to count only the time that users are logged on to Facebook and actively using their desktop computers, ignoring their Facebook activities like status updates, uploads and downloads that will consume additional energy in the network infrastructure and data centers.

Putting all this together works out to 4.2 million metric tons of CO2e per year for all Facebook users. (The actual emissions are likely to be higher, but that depends on a lot of factors ignored here.) This carbon footprint is equivalent to the annual emissions from a million passenger cars in the US.

I know, it is not fair to focus just on Facebook, but I am just using it as an example to understand the footprint of social networking today and how this might change if someday 3-4 billion people end up on social networking sites. I will get back to this topic soon and report on a more rigorous, defensible analysis. For now, this remains a quick-and-dirty initial estimate and a starting point for further exploration.

December 03, 2009

A number of states are considering a Low Carbon Fuel Standard (LCFS) following California's adoption of its own standard earlier this year. An LCFS regulates the carbon intensity of transport fuels. It reaches as far upstream into the fuel supply chain as possible and focuses on the relatively small number of oil refiners and importers. Each company works under the constraint of a maximum carbon intensity (g of CO2e per MJ of fuel energy). This cap declines annually in order to reduce total emissions, and allows trading of emission credits between oil refiners, biofuel producers and electric utilities. Adding the right biofuels to the mix could reduce a suppliers average carbon intensity. This, of course requires a full life-cycle assessment of each fuel (well to tank + tank to wheels, including challenging issues such as co-product allocation and indirect land-use changes) in order to establish its carbon intensity. This is the first public policy initiative that codifies life-cycle assessment principles into law! More in an excellent article by Sperling and Yeh in Issues in Science and Technology.

December 01, 2009

The future of lighting is likely to be LED based. A life-cycle assessment study by OSRAM Opto Semiconductors compares the life cycle environmental impacts of three types of lamps: a 40W incandescent lamp, an 8 W compact fluorescent lamp (CFL), and an 8 W LED lamp with 6 LEDs -- compared on the basis of luminous flux (345-420 lumen) as well as color temperature and rendering, and a lifetime of 25,000 hours. This translates to 25 incadescent lamps, 2.5 compact fluorescent lamps and 1 LED lamp. Here are their results in Kg of CO2e:

Manufacture

Use

Incandescent

3.5

564

Compact fluorescent

2.2

113

LED

2.4

113

The use phase dominates (manufacturing contributes less than 2% of life-cycle GHG emissions) and the LED lamp is competitive with CFL based on current technologies.